Why Lactic Acid is My Winter BFF
I live in Chicago, which is infamous for its frosty winters. Because it’s so cold outside, my HVAC dries out the indoor air as it heats my apartment. When I first moved to Chicago from Georgia, I struggled with dry skin in the winter. Over time I’ve developed a routine that keeps my skin looking nice even if it’s 0F/-17C outside. And one key component is The Ordinary’s The Ordinary Lactic Acid 5% + HA.
Lactic Acid: Both humectant and exfoliant (and antioxidant/anti-aging/anti-acne!)
Most people know lactic acid, an alpha hydroxy acid (AHA), for its exfoliating properties. Specifically against uneven skin tone conditions like melasma and hyperpigmentation. But fewer people know that lactic acid is also a humectant. Humectants are chemicals that attract and hold on to water [1], keeping the skin moisturized.
Science shows that lactic acid is a very effective humectant and also works as an antioxidant (protects against aging/browning) [2]. One thing that surprised me to learn was that some studies show lactic acid is more effective against acne then the acid typically used for acne (salicylic acid) [2].
This makes lactic acid great for cold, dry winters, as well as easier on sensitive skin than other acids like beta hydroxy acids (BHA) such as salicylic acid.
The most famous humectant these days is probably hyaluronic acid (HA), which is also in The Ordinary’s lactic acid product, so you get two humectants in one product.
Don’t use humectants like lactic acid without the sealing/moisturizing step
The downside of humectants is that if the air is dry, they can’t get any water from it, and theoretically could pull water from your skin instead. The humectants need their own protection from drying out [4]. Emollients in traditional moisturizers are very good at this, as they form a protective layer that prevents water from getting out.
That’s why The Ordinary officially recommends a “seal” step of moisturizer in their routines. For example their The Ordinary Natural Moisturizing Factors + HA contains Caprylic/Capric Triglyceride, a mix of fatty acids that prevents “trans-epidermal water loss” which is a fancy way of saying it traps water.
Unofficially, probably any moisturizer would work, or even just plain oils.
The other downsides of lactic acid: don’t use during the day and don’t layer with these other products
In our routine builder tool we follow The Ordinary’s official product recommendations and don’t allow you to put lactic acid in routines that:
- Are for daytime, since direct acids like lactic acid can increase sun sensitivity (sun damage and even burns)
- Include products that The Ordinary doesn’t recommend layering with 7 types of/specific products including direct acids such as retinoids (can make skin too sensitive) or peptides (can degrade peptides and make them ineffective)
If you want to use products that don’t mix nicely with lactic acid at night, you can develop 2-3 night routines with different products.
Example routines
If you want to use products that don’t mix nicely with lactic acid at night, you can develop 2-3 night routines with different products. For example
Night 1: Simple Lactic Acid
Night 2: Simple Copper Peptides routine
Night 3: Simple Retinoids routine
Night 4: Simple Copper Peptides routine
The peptides routines in between are to give your skin a break between the potentially irritating acid and retinoid routines.
Lactic Acid 5% + HA vs. Lactic Acid 10% + HA
The main difference between the 10% and 5% is 10% is stronger. I’d recommend starting with 5% and only using 10% if you have used 5% up an entire bottle of 5% without any problems.
5% is likely good for most people and most of the studies I read used similar concentrations.